1. Field of the Invention
The present invention relates to an optical module that installs an optical module with an identifying mark that is able to be inspected even after the optical device is installed in the optical module.
2. Related Background Arts
The manufacturing of the optical module includes a process to cleave a semiconductor wafer to obtain so many numbers of device chips, to assemble respective device chips on a stem of the optical module and to enclose the device chip within a package by assembling the cap with the stem. The optical module thus assembled is installed within an optical transceiver as a transmitter optical subassembly (TOSA) or a receiver optical subassembly (ROSA).
Recent optical communication system has continuously requested further performance for the TOSA and the ROSA, which inevitably reduces the process margin and the yield of the optical device. Moreover, the optical device with an optical transmitting function, namely, a semiconductor laser diode generally shows a variation in the performance thereof after it is packaged. Therefore, it is necessary for the stability of the production of the optical module to distinguish the optical device, or the semiconductor chip even after the package enclosed the chip therein.
A PCT application internationally published as WO2000/057458 has disclosed a semiconductor device with information to identify the device, such as a number of the production lot, a number of wafers, and a position of the chip within the wafer. Such information is reflected in patterns formed on the top surface of the device chip to be inspected during the assembling process of the device chip. The information thus appeared in the device chip may be fed back to the wafer process to increase the process stability.
However, the identifying pattern disclosed in the prior art is formed on the top surface of the device chip, the pattern becomes unrecognizable after the device chip is enclosed within the CAN package. Therefore, additional information or a conversion table that relates the device chip within the CAN package to the wafer process is necessary, which complicates the management of the production.